gadolinium

gadolinium

(gădəlĭn`ēəm), metallic chemical element; symbol Gd; at. no. 64; at. wt. 157.25; m.p. 1,312&degC;; b.p. 3,233&degC;; sp. gr. 7.898 at 25&degC;; valence +3. Gadolinium is a malleable, ductile, lustrous silver-white metal with a hexagonal close-packed crystalline structure at room temperature. It is a rare-earth metalrare-earth metals,in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually considered a rare-earth metal......Click the link for more information. found in Group 3 of the periodic tableperiodic table,chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled.....Click the link for more information.. Although the metal does not tarnish in dry air, in moist air an oxide film forms; the film flakes off, exposing more metal to oxidation. Gadolinium reacts slowly with water and dissolves in dilute mineral acids. It occurs in nature in its salts and especially as the oxide, gadolinia, a rare earthrare earths,in chemistry, oxides of the rare-earth metals. They were once thought to be elements themselves. They are widely distributed in the earth's crust and are fairly abundant, although they were once thought to be very scarce......Click the link for more information.. It is a component of the minerals gadolinite, monazite, and bastnasite. Naturally occurring gadolinium is a mixture of seven isotopes; ten additional isotopes are known. Although gadolinium absorbs neutrons more effectively than does any other known substance, this property is caused by two isotopes that are present only to a limited extent in natural gadolinium. Gadolinium has found some use in control rods for nuclear reactors; it has also been used as a "poison" in nuclear fuels, added to control the initial rapid reaction and "burning out" as the reaction proceeds. Gadolinium metal can be prepared by reduction of anhydrous gadolinium fluoride with calcium metal. Gadolinium has unusual magnetic properties. At room temperature the metal is paramagnetic, but it becomes strongly ferromagnetic when cooled. Gadolinium compounds are used as phosphors in the manufacture of color-television picture tubes. Gadolinia, the oxide, was extracted from the mineral gadolinite [for J. Gadolin, a Finnish chemist] in 1880 by J. C. G. de Marignac; in 1886, P. E. Lecoq de Boisbaudran independently isolated the oxide from Mosander's "yttria."

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